1. Field
The embodiments discussed herein are related to a data communication apparatus, a data communication system, and a data communication method that are applied to a system that automatically reads a usage amount of electricity or the like.
2. Description of Related Art
In recent years, a form of applying an ad hoc communication in which a plurality of wireless stations mutually communicate wirelessly and perform multihop communication to establish a network, as a network infrastructure of automatic meter-reading for electricity or the like has been proposed. By applying the ad hoc communication, it is aimed to provide an automated meter-reading system that covers a wide range of areas while keeping cost of facilities low (for example, TAKAHASHI, Yuji, et al., “Network Technology Supporting an Intelligent Society: WisReed”, the FUJITSU magazine, FUJITSU LIMITED, Vol. 62, No. 3, pp. 348-355, September, 2011).
As a related wireless station that performs the ad hoc communication, a node device that is described in Japanese Patent No. 4820464 has been available. This node device is configured to be able to select an appropriate path even if a network topology has not been identified. This node device determines, when transmitting (including transfer) a frame addressed to a certain node device, which one among adjacent nodes (node devices positioned adjacently) the frame is to be transmitted, based on priority of each adjacent node prescribed for each destination of the frame, and transmits the frame to the determined node. Moreover, when transmission fails, a new transmission destination is determined from among remaining adjacent nodes excluding the adjacent node for which the transmission has failed. In transfer operation of a frame received from an adjacent node, when transmission fails even if transfer to all adjacent nodes excluding the adjacent node of the source of the received frame has been attempted, that is, when no path to a destination node is present, the frame is returned to the adjacent node of the source.
The node device disclosed in Japanese Patent No. 4820464, as described, attempts transmission/transfer of a frame to all adjacent nodes at the time of transmission or transfer of a frame. In transfer, when transmission to all adjacent nodes fails (when no path to a destination node is present), the frame is returned to a preceding node (source node), and the preceding node attempts retransmission/transfer of the frame to other paths. However, if the operation to return a frame to a preceding node increases, a problem arises that time in which the frame stays on the network increases.
Furthermore, when a destination node has a failure, or when all nodes adjacent to the destination node have a failure, although it is in a state in which a path to the destination node is not available, transfer of the frame among nodes around the node having a failure and transmission of the frame to the node having a failure are repeatedly performed. As a result, a problem arises that useless frame transmission occurs to consume communication resources unnecessarily.